LOCATION 



459 



the country until you reached North Platte, Nebraska, again your 

 watch would need to be set back one hour. On arriving at Sparks, 

 Nevada, another hour would be gained. From the time you leave 



FIG. 351. A map showing the proposed standard time belts of the world. We 

 have seen how the distance traveled by a ship each day is found by com- 

 paring the local or ship's time with Greenwich time, the ship's time being 

 determined by the position of the sun or stars and the Greenwich time by 

 the vessel's chronometer. From this it will be noted that the difference 

 east or west between any two places is merely the difference between the 

 two local times expressed in degrees. No way has ever been found, how- 

 ever, for making a ship's chronometer keep exactly correct time. At times 

 the clock's error is such as to render the accurate finding of the ship's 

 position impossible; and in such cases, when the vessel is near land, dis- 

 astrous results may follow. With the scheme of the International Con- 

 ference the wireless signals will act as a check on the chronometers. The 

 great importance of this may be realized when it is remembered that an 

 error of one second in calculating the time at sea means an error, in de- 

 termining the ship's position, of something like 1000 feet. 



New York to your arrival in San Francisco, California, it would be 

 necessary for you to set your watch back three hours. 



This arrangement of time for our country is for convenience. 

 When the sun is on the meridian of any town it is 12 o'clock noon, 



